William Haddow Pettit (1885-1985) was a Christian missionary to Bangladesh with the New Zealand Baptist Missionary Society from 1910-1915, and a leader of the fundamentalist/evangelical movement in New Zealand in the 1920s and 1930s. He founded the Crusader Union of New Zealand in 1930 after hosting IVF preacher Howard Guinness, and played a leading role in the formation of the Inter-Varsity Fellowship of Evangelical Unions (NZ) (now known as Tertiary Students Christian Fellowship) in 1936.